2007年5月29日 星期二
2007年5月28日 星期一
IT Numbers
Java 19.14%
C 15.15%
C++ 10.11%
PHP 8.74%
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Perl 6.15%
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Javascript 3.07%
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C 15.15%
C++ 10.11%
PHP 8.74%
Visual Basic 8.43%
Perl 6.15%
Python 3.78%
C# 3.66%
Javascript 3.07%
Ruby 2.63%
Delphi 2.13%
SAS 2.08%
PL/SQL 1.98%
D 1.35%
ABAP 0.73%
Lisp/Scheme 0.70%
Ada 0.68%
Foxpro/xBase 0.64%
Fortran 0.63%
COBOL 0.63%
2007年5月22日 星期二
Electrohydrodynamic (EHD) flow
Electrohydrodynamic (EHD) flow around a charged spherical colloid near
an electrode was studied theoretically and experimentally to understand the
nature of long-range particle–particle attraction near electrodes. Numerical
computations for finite double-layer thicknesses confirmed the validity of an
asymptotic methodology for thin layers. Then the electric potential around the
particle was computed analytically in the limit of zero Peclet number and thin
double layers for oscillatory electric fields at frequencies where Faradaic
reactions are negligible. Streamfunctions for the steady component of the EHD
flow were determined with an electro-osmotic slip boundary condition on the
electrode surface. Accordingly, it was established how the axisymmetric flow
along the electrode is related to the dipole coefficient of the colloidal
particle. Under certain conditions, the flow is directed toward the particle and
decays as r?4, in accord with observations of long-range particle aggregation.
To test the theory, particle-tracking experiments were performed with
fluorescent 300 nm particles around 50μm particles over a wide range of
electric field strengths and frequencies. Treating the particle surface
conductivity as a fitting parameter yields velocities in excellent agreement
with the theoretical predictions. The observed frequency dependence, however,
differs from the model predictions, suggesting that the effect of convection on
the charge distribution is not negligible as assumed in the zero Peclet number
limit.
an electrode was studied theoretically and experimentally to understand the
nature of long-range particle–particle attraction near electrodes. Numerical
computations for finite double-layer thicknesses confirmed the validity of an
asymptotic methodology for thin layers. Then the electric potential around the
particle was computed analytically in the limit of zero Peclet number and thin
double layers for oscillatory electric fields at frequencies where Faradaic
reactions are negligible. Streamfunctions for the steady component of the EHD
flow were determined with an electro-osmotic slip boundary condition on the
electrode surface. Accordingly, it was established how the axisymmetric flow
along the electrode is related to the dipole coefficient of the colloidal
particle. Under certain conditions, the flow is directed toward the particle and
decays as r?4, in accord with observations of long-range particle aggregation.
To test the theory, particle-tracking experiments were performed with
fluorescent 300 nm particles around 50μm particles over a wide range of
electric field strengths and frequencies. Treating the particle surface
conductivity as a fitting parameter yields velocities in excellent agreement
with the theoretical predictions. The observed frequency dependence, however,
differs from the model predictions, suggesting that the effect of convection on
the charge distribution is not negligible as assumed in the zero Peclet number
limit.
2007年5月7日 星期一
Primes
每日一試
首頁 每日一試 數學資訊 軟體介紹 數學討論 會員專區
Chapter 1 The unique factorization theorem
1 Primes
We assume as known the positive integers 1,2,3,..., the negative integers -1,-2,-3,..., and zero, which we reckon as an integer. By the non-negative integers we mean the positive integers together with zero. We assume as known the elementary arithemetical operations on integers. An integer a is said to divisible by a nozero integer b, if there an integer c,such that a = bc. We then say that a is an integer multiple or just a multiple of b. An integer p, where p > 1 , is a prime number,or a prime, if its only positive divisors are 1 and p.
2 The unique factorization theorem
If n is an integer greater than 1,then n is a product of primes. The standard form of an integer n,which is greater than 1,is unique.
首頁 每日一試 數學資訊 軟體介紹 數學討論 會員專區
Chapter 1 The unique factorization theorem
1 Primes
We assume as known the positive integers 1,2,3,..., the negative integers -1,-2,-3,..., and zero, which we reckon as an integer. By the non-negative integers we mean the positive integers together with zero. We assume as known the elementary arithemetical operations on integers. An integer a is said to divisible by a nozero integer b, if there an integer c,such that a = bc. We then say that a is an integer multiple or just a multiple of b. An integer p, where p > 1 , is a prime number,or a prime, if its only positive divisors are 1 and p.
2 The unique factorization theorem
If n is an integer greater than 1,then n is a product of primes. The standard form of an integer n,which is greater than 1,is unique.
2007年5月2日 星期三
2的11次方可以用咩方法計算最快ar?
2的11次方可以用咩方法計算最快ar?
ANS:
2的10次方是 1K.
1K = 1024.
所以 2048.
2 的 10 次方 = 1K
2 的 20 次方 = 1M
2 的 30 次方 = 1G
ANS:
2的10次方是 1K.
1K = 1024.
所以 2048.
2 的 10 次方 = 1K
2 的 20 次方 = 1M
2 的 30 次方 = 1G
在1到100間任選51個數 試證必有一個數可整除另一個數
Fifty-one integers are chosen between 1 to 100
Prove that some one of these divides another
在1到100間任選51個數 試證必有一個數可整除另一個數
拜託有誰會阿~~~~幫幫我吧
Prove that some one of these divides another
在1到100間任選51個數 試證必有一個數可整除另一個數
拜託有誰會阿~~~~幫幫我吧
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